Slurry reactors are well known for carrying out highly exothermic, three phase, catalytic reactions. Usually called "slurry bubble columns" these reactors have a liquid phase in which solid catalyst particles are dispersed or held in suspension by a gas phase bubbling through the liquid phase, thereby creating a slurry. These reactors provide improved heat transfer characteristics for the exothermic reaction, and the bubbling gas provides essentially all of the energy necessary for maintaining the catalyst dispersed in the liquid phase.
Bubble column reactors typically have a multiplicity of tubes suspended within a shell-type housing, the tubes being filed with a heat transfer medium, e.g., steam, which absorbs the heat generated by the exothermic reaction occurring on the shell side of the tubes in the main body of the housing.
Alternatively the reactor can be of a similar multi-tube design housed in a common shell-type housing as previously described but wherein the gas and liquid are passed through the multiple tubes which function as the reactor tubes, with effluent being removed from the upper ends of the reactor tubes and heat transfer fluid is passed through the space along the outside surfaces of the reactor tubes. The reactor tubes can be either multiple individual tubes with spaces between adjacent tubes, or multiple bundles of tubes with spaces between adjacent bundles of tubes.
Likewise the entire cross section of the reactor vessel may have a plurality of shafts disposed within it, the bottoms of said shafts being located above the reaction gas inlet but extending a distance above the top surface of the reaction slurry into the gas disengaging spaces so as to create multiple single columns of standing, non-circulating liquid with catalyst suspended and dispersed in said standing liquid. The reaction zone therefor has multiple single columns, said columns having a common bottom reaction gas introduction zone and a common upper gas disengagement space. To insure proper control of the exothermic process additional tubes can be inserted into or between the multiple single columns to function as heat exchangers.
As previously stated, in slurry bubble columns, the catalyst particles are suspended by the gas entering the bubble columns through bottom sited distributors. Often, catalyst particles in these reactors are non-uniformly distributed in the axial direction of the reactor vessel within the range of gas velocities of interest to the practitioner. Under these conditions the reactor operation is limited by "hot spots" which are formed by zones of catalyst near the bottom of the column where the highest catalyst concentration is found or in stagnant eddy current circulating zones. Non-uniform catalyst distribution also contributes to non-uniform catalyst aging and inefficient catalyst utilization insofar as the reaction progresses only when reactants are in contact with catalyst. In hydrocarbon synthesis processes such "hot spots" force the reactor to operate under less than maximum efficiency conditions.
It would be an advance if, in whatever configuration the reaction vessel may take, catalyst within the slurry reaction vessel could be more uniformly distributed and circulated so as to insure more even catalyst aging in the course of the reaction, more effective use of the catalyst by insuring a higher probability that the maximum amount of available catalyst is circulating in the reaction zone to promote the reaction by eliminating stagnant zones of standing catalyst.